Signal-processing circuits, such as analog-to-digital converter circuits, may under particular circumstances, exhibit tonal behavior. That is, the signal-processing circuits may generate tones, which may be undesirable for an intended application. For example, a delta-sigma modulator circuit may, in certain circumstances, output quantization noise, including idle-channel noise. Also for example, a delta-sigma modulator circuit may, in certain circumstances, exhibit periodic (e.g., tonal) behavior. Even in circumstances where such noise is not directly perceivable by a user, such noise may adversely affect circuit performance.
Various attempts have been made to reduce tonal behavior in signal-processing circuits. For example, in various analog-to-digital converter circuits, attempts have been made to introduce a random signal into the circuit to disrupt periodic circuit behavior. An example of this may be found in “Delta-Sigma Data Converters, Theory Design and Simulation,” by Norsworthy et al., and published by IEEE Press, which shows introducing a random analog signal into a delta-sigma modulator circuit.
Introducing such a random analog signal into a circuit may not be an optimal solution, depending, for example, on the particular circuit and practical circuit design considerations. Accordingly, attempts have been made to introduce a random digital signal into a circuit to disrupt periodic circuit behavior. An example of this may be found in U.S. Pat. No. 6,577,257 to Brooks, the content of which is hereby incorporated herein by reference in its entirety. The U.S. Pat. No. 6,577,257 shows a system and method for introducing a digital dither signal into a delta-sigma modulator circuit to disrupt periodic behavior.
Introducing a digital signal (e.g., a digital dither signal) into a signal-processing circuit to disrupt periodic behavior or to control other noise-producing aspects of a signal-processing circuit may result in decreased circuit performance and undesirable components in an output signal of the signal-processing circuit. That is, introducing such a digital signal into a signal-processing circuit may solve one problem while creating others.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with the present invention as set forth in the remainder of the present application with reference to the drawings.